Positive electrode active material, and lithium secondary battery using same

Abstract

A positive electrode active material for lithium secondary batteries disclosed herein comprises a lithium transition metal oxide of a layered structure, represented by formula Li1+αNixCoyMnzCaβMγO2 (where −0.05≦α≦0.2, x+y+z+β+γ≅1, 0.3≦x≦≦0.7, 0.1≦y≦0.4, 0.1≦z≦0.4, 0.0002≦β≦0.0025, 0.0002≦β+γ≦0.02, and in a case where γ>0, M is absent or represents one, two or more elements selected from the group consisting of Na, Mg, Al, Ti, V, Cr, Zr, Nb, Mo, Hf, Ta and W). The tap density of the positive electrode active material ranges from 1.8 to 2.5 g / cm3.

Description

TECHNICAL FIELD[0001]The present invention relates to a positive electrode active material for lithium secondary batteries. The present invention relates further to a lithium secondary battery obtained by using the positive electrode active material.[0002]The present international application claims priority based on Japanese Patent Application No. 2013-11524, filed on Jan. 24, 2013, the entire contents whereof are incorporated herein by reference.BACKGROUND ART[0003]Lithium secondary batteries boast smaller size, lighter weight and higher energy density than existing batteries and exhibit improved input-output density. Accordingly, lithium secondary batteries are preferably used as so-called portable power sources in personal computers or mobile terminals, and as high-output power sources installed in vehicles.[0004]Such lithium secondary batteries are generally used in a state where voltage is controlled so as to lie within a predefined region (for instance, 3.0 V to 4.2 V). Howev...

AI Technical Summary

Benefits of technology

The present invention provides a lithium secondary battery with a positive electrode active material that can improve battery performance and reliability during overcharge. The battery has a current interrupt device that is activated when the battery internal pressure rises, which ensures the safety and reliability of the battery. The positive electrode material can also be used to produce a power source for vehicles.

Problems solved by technology

However, studies by the inventors have revealed that a concern of delayed activation of the CID, during overcharge, arises depending on, for instance, the properties of the positive electrode active material that is used.

A further concern arose in that gas might not be discharged smoothly from an electrode active material layer, due to narrowing diffusion paths of the generated gas.

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